Deciphering biotransformation of anthraquinone electron shuttles in Rheum palmatum L. for value-added production

Abstract

BackgroundRecent findings indicated that electron mediating characteristics of electrochemical catalysis would enhance disease-treating efficacy of herbal medicine. In particular, biomass energy-amplifying and electron transfer-stimulating medicines could even treat not only brain-associated diseases, but also virus-caused infections. Exploring different electron shuttle (ES)-bearing medicinal herbs for biorefinery should have potentials to develop value-added production (e.g., medicated diet). MethodsMicrobial fuel cells (MFCs) were used as the bioenergy-evaluating platform to select the most promising anthraquinone (AQ) ES-abundant herb. Optimal conditions of water and ethanol extraction were determined to maximize bioenergy content of resultant extract. According to HPLC, MS/MS and TAC analyses, serial acclimation to select effective rhubarb-degrading bacteria was implemented to maximize the product formation. Significant findingsRheum palmatum L. was the most favorable AQ-plentiful medicinal herb to exhibit bioenergy-stimulating activities. Extraction at higher ethanol % could obtain the maximal recovery of AQ content; however, an increased inhibition was resulted as MFC results indicated. With 3-4 cycles of acclimation using appropriate food-originated microbes, the production of aloe-emodin and chrysophanol increased ca. 400% and 270%, respectively. To the best of our knowledge, this first-attempt study provided a novel bioenergy perspective to maximize AQ production of rhubarb fermentation. Moreover, significant reduction of biotoxicity potency should be top-priority concern to guarantee this GRAS production.